The present invention relates to a method of operating an automated blood pressure measuring apparatus. More specifically, the present invention relates to a method of operating an automated non-invasive blood pressure (NIBP) monitor to estimate a patient's blood pressure during the initial cuff inflation to enhance the performance of the NIBP monitor.
Automated blood pressure monitoring has rapidly become an accepted and, in many cases, essential aspect of human treatment. Such monitors are now a conventional part of the patient environment in emergency rooms, intensive and critical care units, and in the operating theater.
The oscillometric method of measuring blood pressure involves applying an inflatable cuff around an extremity of a patient's body, such as a patient's upper arm. The cuff is inflated to a pressure above the patient's systolic pressure and then the cuff pressure is reduced either continuously or incrementally in a series of small steps. A pressure sensor measures the cuff pressure, including the pressure fluctuations resulting from the beat-to-beat pressure changes in the artery under the cuff. The data from the pressure sensor is used to compute the patient's systolic pressure, mean arterial pressure (MAP) and diastolic pressure
An example of the oscillometric method of measuring blood pressure is shown and described in U.S. Pat. Nos. 4,360,029; 4,394,034; and 4,638,810, which are commonly assigned with the present invention.
During the use of a conventional NIBP monitoring system, the blood pressure cuff is placed around the arm of a patient and is inflated to a pressure that fully occludes the brachial artery to prevent blood flow. The cuff is then progressively deflated and a pressure transducer detects pressure pulses as blood begins to flow past the pressure cuff. As can be understood, the selection of the initial inflation pressure determines the amount of time and deflation required before the NIBP system begins to detect cuff oscillations and blood flow. If the initial inflation pressure is selected well above the systolic blood pressure for the patient, the NIBP system over inflates the blood pressure cuff, resulting in patient discomfort and extended measurement time. Alternatively, if the initial inflation pressure is selected below the systolic blood pressure for the patient, the blood pressure cuff must re-inflate to obtain an accurate reading. Therefore, it is desirable to estimate the patient's blood pressure to control the cuff inflation and deflation to enhance the performance of a NIBP system.